1. Field of the Invention
The present invention relates to a polishing pad, a polishing method and a method of forming a polishing pad. More particularly, the polishing pad can provide a different slurry flow distribution.
2. Description of Related Art
With the progress of the industry, a planarization process is often adopted as a process for manufacturing various devices. A chemical mechanical polishing (CMP) process is often used in the planarization process in the industry. General speaking, the chemical mechanical polishing process supplies slurry having a chemical on the polishing pad, applies a pressure on the substrate to be polished to press it on the polishing pad, and provides a relative motion between the substrate and the polishing pad. Through the mechanical friction generated by the relative motion and the chemical effects of the slurry, a portion of the surface layer of the substrate is removed to make the surface flat and smooth so as to achieve planarization.
FIG. 1 is a schematic top view of a conventional polishing pad. FIG. 1A is a cross-section view of the polishing pad taken along a line A-A′ in FIG. 1. Referring to FIG. 1, a polishing pad 100 includes a polishing layer 102 and a plurality of circumferential grooves 104. The polishing layer 102 is in contact with a surface of a substrate 105 (e.g. a wafer). The plurality of circumferential grooves 104 is disposed in the polishing layer 102 in the manner of concentric circles. The circumferential grooves 104 are used to contain slurry. When the polishing process is performed, the polishing pad 100 moves in a rotational direction 101, for example, a counterclockwise direction as shown in FIG. 1. At the same time when the polishing pad 100 rotates, the slurry is continuously supplied to the polishing pad 100 and flows between the polishing layer 102 and the substrate 105.
As shown in FIG. 1A, part of the slurry flows to the surface of the polishing layer 102 through the centrifugal force generated from the rotation of the polishing pad 100, as shown in a flow direction 103. However, most of the slurry 108 is still contained in the circumferential grooves 104 and only a small portion thereof flows to the surface of the polishing layer 102. The distribution of the slurry has an effect on polishing characteristics during the polishing process.
Therefore, it is needed to provide a polishing pad which can provide a different slurry flow distribution for industry in response to the requirements of various polishing processes.